Multiplex transmitter



. W. P. STUNZ MULTIPLEX TRANSMITTER June 30, 1931 3` Sheets-Shed l Filed Jan'. 6, 1928 INVENTOR.

June 30, 1931. w. P. sTuNz 1,812,570

MULTIPLEX TRANSMITTER Filed Jan. 6, 1928 5 Sheets-Sheet 2 d ATTORNEY.

June 30, 1931. w. P. sTUNZ MULTIPLEX TRANSMITTER Filed Jan. e, 1928 3 Sheets-Sheet 3 f. INI/NTOR. r A

A TTORNE Y.

Patented June 1931 f UNITED STATES PATENT OFFICE .i

`lTlILllfIAIlltI P. STUNZ, F LANSDOWNE, MARYLAND, ASSIGNOR TO SAFE DEPOSIT' AND .'TRUST COMPANY OF BALTIMORE, rA CORPORATION 0F MARYLAND, AS TRUSTEE UNDER THE WILLy GEORGE R. WEBB MULTIPLEX TRANSMITTER Application led January 6, 1928. Serial No. 244,930.

My invention relates to telephonie transmitters, and more particularly to such instruments for transmission of sound vibrations, especially of t-he character of musical vibrations as taken from a' record. One object of the present invention is to increase the capacity of the output of the electrical currentv generating elements of the transmitter so that the volume of vibrations emitted from a receiver will be materially increased without distortion that would impair the clearness of delivery of the received vibrations and whereby the instrument has the capacity to fill or supply an auditorium chamber of larger area with themusical or sound vibrations with greater clearness or distinctnessV than previously.

It hasl also for another obj ect to eliminate entirely or to a material extent the objectionable and disconcerting metallic or scratchy noises resulting from contact of the tracer element or needle with the material or substance of the record from which the musical or other vibrations are received and transmitted. It has also for other objects to provide improved features in various parts of the transmitter unit whereby material advantages are gained as will be hereinafter made to appear.

To the accomplishment of the foregoing, the invention consists in the features hereinafter particularly described and then sought to be clearly defined by the claims, reference being had to the accompanying drawings forming a part hereof, and in which Figure 1 is aside elevation, with front and rear cover plates removed;

' Figure 2 is a sectional plan, taken on line 2 2 of Fig. 1;

F Figure 3 is a cross-section, on line 3-3 of Figure v4 is a similar view online 4 4 of Fig. 2; Y Figure 5 is a sectional view on line 5-5 of Fig. 3;

Figure 6 is a detail view, showing the spider and vibrating arm, or lever;

F'gure 7 A's a detail perspective diagrammatical view, showing the direction of the electrical circuits;

Figure 8 is an enlarged vertical section, taken ,on line 8-8 of Fig. 1;

Figure 9 is a detail perspective view of flat fulcrum spring; f Figure 10 is a detail view, showing a modication of the fulcrum spring;

Figure 11 is a sectional view taken on line 11-11 of Fig. 10;

Figure 12 is a diagrammatic view, showing a lVheatstone bridge circuit with Aeight granular-carbon chambers. In the drawings, the letter A designates in general the electrical current or circuit creatlng unit; B the record tracer or reproducing needle unit; C the arm which connects the reproducing needle unit with the electrical current or circuit unit; and D the member by which the units A, B, and C, are sustained from a suitable support and which permits a vertical Vas well as a horizontal movement of the units A, B, and C to conform to the impressed recorded undulations of the record and 'to any surface irregularities in the plane of the record.

The unit A comprises a casing formed of end plates 1, preferably brass, and intermediate member 2`, preferably brass, connecting the end plates. Within the casing are two bridge plates 3, preferably of brass, secured in position by rods 4, to which the plates are connected, passing through the end plates 1 and provided with spacing sleeves 5.

Within the casing or shell there is'containedV a plurality of granular-carbon chambers or cups, eight of such chambers being illustrated, and designated respectively by the numerals 7 t0 14. One set, consisting of four of the chambers 7 8, 9 and 10, is supported from a plate or block 15, formed preferably of balrelite, or other suitable insulating material, and the other set consisting of chambers 11, 12, 13 and 14 supported from a similarly formed plate or block 16. The chambers are disposed so that one set of four will face the other` set of four, as illustrated.

Each chamber is made up of a base-member 17, of a suitable electrical conductor material, preferably brass, which has a threaded stem 18 passing through the plate and secured by a nut 19; a stationary electrode 20, which may be a carbon-button, attached by a screw 22, or otherwise, to the inner face o'f the base-member 1?; a movable electrode 23, which may be a carbon-button; a granular carbon containing space or chamber 24 between the fixed and movable electrodes, and an enclosing wall 25, say of felt. The back and front blocks 15 and 16 carrying the granular carbon chambers or cells are tied together by the metal posts 26, 2T, 28 and 29. Between the bridge-plates 3 and the plates or blocks 15 and 16, respectively, from which the granular carbon cells or electrodes are supported, there are placed cushioning pads 30 `ot' sott rubber which relieve to agreater or less extent disturbance of the carbon granules from movements of the supporting parts of the transmitter. Between'the insulated plates or blocks 15, 16 and the basemembers of the several granular carbon cells there are placed electrical conductor-plates 31, 32, 33 and 34, the two sets ot connector'- plates having substantially the outline illustrated and one pair of plates of each set having its plates oined by, a connecting-neck 35.

In the space between the two sets of granu lar carbon cells, four cells to each set, there is positioned an oscillatory spider E, preferably made ot aluminum, having four radial arms 36, 37, 38 and 39. This spider is sup-l ported to oscillate by the adjustable threaded pivot pins 40 threaded in bearings 41 attached to the face of plate orbloclr 16. The spider carries two sets of movable electrodes 23, say carbon-buttons, tour electrodes' to each set, corresponding' to the two'setsof granular carbon cells, four cells tol each set of electrodes (four in number) lying op'- posite one face of the spider andthe-other set (four in number) opposite the other face, the electrodes being carried by the arms o-i the spider and suitably connected thereto, say by the screws 43, insulated therefrom and from spacing washers 44 by an insulating bushing 45 and mica washers 47. VrThe two upper movable electrodes of each=set` will be connected with the companion two lower elec# trodes by thin metal conductor strips 46 which will be insulated from the spider'arms by mica washers 47.

By the employment of the oscillatory spider' having a set oi four granular carbon cells on one side and four cells on the other side, the granular carbon in two of the cells on one side is compressed andthe carbon in two cells on the other side is likewise compressed while the carbon of the other cells, two on each side, is released from compression, so that there will be sent out to the receiver or loud speaker an increased volume of current from the cells whose granular carbon is under compression, the discharge oi the current to the loud speaker or receiver alter- 7 nately changing from positive to negative,

being an undulatory alternating current of increased volume and resulting in a clearer reproduction 'of sound vibrations throughout a larger area of the receiving auditorium.

The sound vibrations thus transmitted are received from a record through the following instrumentalities. The numeral 48 designates a lever, suitably connected at one end to the oscillatory spider E andhavingcon'- nected to its other end a tracer or'reproducing needle 49 by a resilient strip 50 connected to the end of the lever and having elastic washers 51 on each side where connected to the lever. The tracer 49 is attached to a member 52, to which the resilient strip is connected, andi supported on alight spring-metal member 53 attached, sayibyscrews 54', to an 'inertia member' which: may bei supported by.4 a tubular arm 56 projecting. from the unit A which carries the granular carbon` cells` and the sev-eral movable electrodes; Theinertia member owingto its-massfcannotlrespond to ahigh rate o'tvibration andhence'provides or functions as a relativelyifiiied' point for the iulcrum of'the vibrating'member` 52.2tliat carries the tracer'. 49 which sensitivelyf res sponds to the vibrations derivedl from' the record. Theannoying scratch more'ori less observable Iin reproducing `vibrations frome record are `due int an objectionable f degreerto the initial vibrations-received by the'ftra'eer needle from the record and that'iprovision is made :for absorbingthese initial'vibrations until they are eliminated orfovercomeiorfdisf sip'ate'd'` by the' greater volume'offreproduce'd vibra-ti ons in the rotation-` of 'the recordrthey will be practically prevented? fnom'i being neticedv in transmission ot the reproduced vibrations so thatthefinal fdi'striliutionfofxthe vibrations will be clearer and free from'ltire initial scratchy reproduction.V This desired result is -eiected byproviding for tliei tracer needlefa variablefulcrumwhich provides' Jor taking care` of 1 these initial vibrations so that only the greaterdominating vibrationsproduced f from the record aire' transmitted'to. tlie receiver' or'loud speaker;` This', innthepres ferr-ed formof the inventionyis accomplished by providing the resilient` :FulcrumA member 53, which 1 inthe preferred' embodiment' .com sists ofa relatively thin springplate'5'3`l to which the` member 52 carrying the* tracer needle '49 is'attached, say byv rivets' 57. so that by movement of the member 52,.a=torsionis set upin the sprin'g'plate suiiicientlto absorb the initial scratch vibrations andire-V sults Vin only the excessor' dominatin'gvibrations being transmitted through the leveri48 to' thel oscillatory spider and carbon'. cell'sof the transmitter unit A and thence to line. The best results of th'islf'eature are obtained by placing or settingthe' broadsideoff the resilientffulcrum member 53, afs distinguished from itsl edge,v towards or'iacing` the* side vibratory movements of the tracerf'n'eedle? tending from one of the end-plates l by which the unit is pivotally supported from a post which has a reduced end 7l so as to tit in a bracket or other support (not shown) whereby the unit A and associated parts is capable of being swung laterally and also in a vertical plane to conform to the side movements of the tracer needle and to provide for surface irregularities in the plane of the record.

lVhile I have illustrated and described with particularity the preferred details of the several parts and their relative relationship, it is to be understood that changes may be made therein, and essential features as sought to be defined by the appended claims may be retained.

Having described my invention and set forth its merits, what I claim is l. A telephone instrument including an oscillating member, a plurality of individual transmitters and their electrodes responsive to received vibrations, a plurality of the transmitters being placed on each side of the oscillating member, a lheatstone circuit inclusive of the transmitters and in which the transmitters are disposed so that a plural number in one branch of the circuit will be placed under high resistance and a corresponding number in another branch will be simultaneously placed under a reduced resistance, in alternation between the respective branches, whereby an increased output of current to line, alternating between negative and positive currents, will be eiective.

2. A telephone instrument including an oscillating member, a plurality of eight individual transmitters and their electrodes responsive to received vibrations, a plurality of the transmitters being placed on each side of the oscillating member, a circuit inclusive of the transmitters and in which the transmitters are disposed with four in one branch of the circuit and four in another branch and arranged so that a. plural number of the transmitters in one branch will be under high resistance and a corresponding number in the other branch will be simultaneously under a reduced resistance, the transmitters in one branch alternating in change of resistance from high to low with the transmitters of the other branch, whereby an increased output of current to line, alternating between negative and positive, will be effected.

3. A telephone instrument comprising a plurality of transmitters and their electrodes responsive to received vibrations, an oscillatory member having sets of transmitters, including four in each set, disposed at opposite faces of said member and operatively connected therewith, a `Wheatstone -circuit in which the transmitters are included, and means for oscillating said member to increase the resistance in a plurality of the transmitters disposed at one face of the member and In testimony whereof I aflix my signature.

WILLIABI P. STUN Z.

Tal 

